by Connie Oswald Stofko
Tender plants, such as tomatoes, peppers and some flowers, need warm temperatures to thrive, so you want your seedlings to be ready to transplant ouside when the weather is warm. If you plant your seeds inside too early, the weather might still be too cold to transplant outdoors.
When should you plant seeds inside to have the plants ready for your garden at the right time?
It depends on what you are planting and where you live in Western New York.
Here are some steps to help you figure out when you should start seeds inside for tender plants.
Read the seed package
Your seed package will tell you how many weeks before your last frost you should plant seeds inside.
When is your last frost?
When your last frost will be depends on where you live in Western New York.
The average date of the last frost in Western New York can range from the end of April for spots on Lake Ontario to the end of May or beginning of June in some Southern Tier areas. See a map of average last spring frosts here from the Northeast Regional Climate Center. The map gives an overall picture of which areas warm up sooner, but it may be difficult to find out where exactly your yard falls on the map.
Put in your Zip Code to find average frost dates for your area from the National Gardening Association. You’ll get a table showing the chances of getting a day with a low temperature of 32 degrees Fahrenheit as well as 36 degrees Fahrenheit.
Note that air temperatures don’t have to be as low as 32 degrees Fahrenheit for your garden to experience a frost. Frost can occur when the temperature falls below 36 degrees Fahrenheit, especially in rural areas, according to the National Weather Service. It is a localized phenomena and can be quite variable across a small area.
Looking at the chart for the Zip Code 14226, there’s a 90 percent chance of the temperatures going down to 36 degrees on April 26, but only a 10 percent chance on May 22. While it’s not as likely that gardens in 14226 could experience a frost on May 22, it could happen.
How to pick a date for your last frost
By now you’ve figured out that there is no exact date that you can depend on for the last frost. Here are some guides to help you choose a date to go with.
How lucky do you feel?
Let’s say you live in 14226. Looking at the chart of the last frost date by Zip Code, there’s a 50-50 chance that you could get a low of 36 degrees on May 9. Are you comfortable taking that risk? Would you rather take a one-in-ten chance and wait until May 22? Or do you want to be safer and put your seedlings out even later?
Pick the date of your comfort zone and count back from there to decide when you will start your seeds.
Use rule-of-thumb guides
Some people around me like to transplant their tomatoes and other tender plants outside on Mother’s Day. Others say the middle of May. Still others use Memorial Day as a rule. Others caution to wait until June to be safe.
Those dates line up more or less with the risk of frost on the Zip Code chart.
You could pick the rule-of-thumb your neighbor or a friend uses to plant outside, then count back from there.
Don’t put all your eggs in one basket
Since we know that we can’t pinpoint the last frost date, and therefore can’t pinpoint the exact time to start seeds for tender plants, give yourself some leeway.
Using the guides above, determine (or guess at) the date to plant your seeds inside. Plant some seeds the week before that date, some seeds the week of that date and some seeds the week after that date.
When it’s time to transplant, watch the weather forecast. If the last frost is earlier than average, you can plant your first set of seedlings outside. If the last frost comes on the average date, you can plant your second set of seedlings. If the last frost is late, you still have some strong seedlings that are ready at the proper time.
More help on planting seeds inside
Lyn Chimera, a Master Gardener with Cornell Cooperative Extension in Erie County, suggests this factsheet with more tips on starting seeds.
For more specific questions, contact the Master Gardeners in your area.